USA: Colorado: Little Snake River Restoration on Three Forks Ranch

Overview

The Three Forks Ranch in Routt County, Colorado was purchased by David Pratt in 1999. Upon acquiring possession of the property, Pratt hired Dave Rosgen of Wildland Hydrology to design and implement a restoration project aimed at improving the hydrology and habitat conditions of a 10.5-mile stretch of the Little Snake River flowing across his property. The largest privately funded river restoration ever undertaken in the U.S., the project included interventions to improve channel dynamics and water quality; streambank stabilization measures; and a host of habitat enhancement actions. Five years of post-project monitoring have shown that, despite higher-than-usual flows in 2005, the river is functioning as expected, and the fishery is benefiting from more dynamic habitat conditions.

Location

Project Stage: Completed

Start Date: 2000-06-27

End Date: 2001-06-27

Primary Causes of Degradation

Agriculture & Livestock

Degradation Description

Three Forks Ranch has been an agricultural enterprise since the 1870’s, when gold played out at nearby Hahn’s Peak in Routt County. The river bottom, being fertile, easily accessible and irrigable, was overused and abused for many years. Overgrazing and haying resulted in the destruction of the willow community along the river banks. Bank degradation soon followed, and a near-irreversible cycle began. Over time, the river channel became wide and shallow, and stream banks became abrupt drops of 3-6 feet into the river. Each spring, snowmelt runoff added to the problem. Water temperatures increased and dissolved oxygen levels declined. These two factors, along with increased sedimentation, greatly reduced the fish habitat in the river.

Project Goals

Monitoring

The project does not have a monitoring plan.

Description of Project Activities: Restoration of the Little Snake River consisted of three main components: modification of the channel to optimize hydrology; stabilization of the streambank to reduce of erosion; and improvement of habitat conditions for the river's fishery.
Hydrologic interventions included deepening and narrowing the channel in several places in order to decrease the width/depth ratio; restoring the natural sinuosity of reaches that had been straightened to facilitate irrigation or road building; and deepening pools in order to create lower water temperatures and increase dissolved oxygen levels. In places where the channel split its flow and both streambanks were eroding, the stream was realigned to occupy only a single channel in order to prevent excess streambank erosion and allow for revetment.
Streambank stabilization and grade control structures were constructed on all stream reaches. Steep, eroded banks were removed in many places, and native cobble was used as a revetment in an effort to eliminate future erosion. Furthermore, approximately 22,000 large boulders were placed along about four miles of river in the form of Rosgen-designed structures--e.g., J-hooks, W-wiers, and cross-vanes--to divert the stream's energy away from the banks and toward the center of the stream. These rock structures also created pools for fish. In areas where the curvature of the channel was too severe, the curvature of the channel bends was reduced. When the massive reconstruction was completed, thousands of mature willows were transplanted on the outside of every meander bend to further stabilize the banks and to provide shade to reduce water temperature. Sods mats were also installed to prevent erosion along many sections of streambank.
Because recreational fishing represents a significant source of income for the ranch, structures designed to provide diversity of habitat--including rearing, spawning and all-season cover--were also installed on all the stream reaches. Converging rock clusters were used to provide in-stream cover in the presence of high bedload streams. The convergence/divergence maintains the scour hole and seams without the associated gravel bar formation. Side channels constructed in the floodplain were designed to have a variety of slopes and velocities. "Beaver pond" channels were designed to provide a 2-foot check every 200 feet in order to create a backwater channel with a constant flow-through diversion. Within the ponds, the depths were designed to be less than 3.5 feet, ranging in width from 40 to 100 feet. Small, Rosgen E4 stream type tributaries with low sediment yield feed the pond adjacent to the Middle Fork of the Little Snake River. Due to this condition, an in-stream pond was designed for native Colorado River cutthroat trout habitat. The outlet structure from the pond was designed as a drop-outlet drain to prevent migration of fish upstream into the system.
Another major phase of the project was to create off-channel fisheries in abandoned river channels using oxbow lakes and interconnecting streams. Irrigation channels were converted to natural steams and "constructed beaver dams" formed oxbow lakes. Seventy-five acres of wetlands were created in this process, along with a diversity of aquatic and terrestrial habitat.
The following are measures taken on specific reaches of the river.
Restoration work performed on two miles of the main stem of the Little Snake River began at the confluence of the North and Middle Fork tributaries. Approximately 56 cross-vanes, 14 J-hook vanes, 3 "W" weirs and 402 converging rock structures were installed. Thirty-seven banks were stabilized with willow/sod mat transplants. 11,500 feet of side channel habitat was created using design criteria. Oxbow lakes were reshaped and/or created, and 42 "beaver dam" plugs for fish habitat in the hay meadow/floodplain and low terraces were constructed.
Restoration work was performed on 10.5 miles of the South Fork of the Little Snake River. Approximately 3 cross-vanes, 420 J-hook vanes, and 990 converging rock structures were installed. 155 banks or bends were stabilized with willow/sod mat transplants. 51,010 feet of channel were realigned using design criteria, and other miscellaneous rehabilitation efforts were completed.
Restoration work was performed on 0.6 miles of the North Fork of the Little Snake River. Approximately 6 cross-vanes, 8 J-hook vanes, and 88 converging rock structures were installed. Five banks or bends were stabilized with willow/sod mat transplants, and 700 feet of channel was converted from a braided to a single-thread channel using design criteria.
Finally, restoration work was performed on 0.9 miles of the Middle Fork of the Little Snake River. Approximately 6 cross-vanes, 32 J-hook vanes, 1 "W" weir and 225 converging rock structures were installed. Two banks were stabilized with willow/sod mat transplants. 3,150 feet of side channel habitat was created using design criteria. Oxbow lakes were reshaped and/or created; one cutthroat trout pond was constructed; and 8 "beaver dam" plugs for fish habitat were created.

Ecological Outcomes Achieved

Eliminate existing threats to the ecosystem: Despite higher-than-usual runoff duration and volume during 2005, the restored reaches throughout the project site remained stable and incurred no system-wide instability or large-scale channel adjustments. The majority of the structures continued to perform as intended, despite relatively long durations of high flows and shear stresses. After five years of observation, monitoring results indicate that the constructed project continues to successfully meet standard definitions of stream and river stability (Mackin 1948, Schumm 1977, Leopold and Bull 1979, Rosgen 1996, Biedenharn et al. 1997). As in other years, some channel adjustments inevitably occurred in 2005; however, these adjustments are not thought to exceed the range of variability observed in comparable, least disturbed natural systems of the region, particularly during system evolution to a new equilibrium state.
The restoration effort has clearly resulted in substantially more pool volume and deep-water habitat with improved potential for riparian shading, lower in-stream temperatures, and higher dissolved oxygen content. Scour by the high flows of 2005 maintained pool volume at a majority of the structures located throughout the project. These pools continue to adequately support the stocked trout population in each of the three major forks of the Little Snake and along the Main Stem of the river. Furthermore, there has been continuing development and re-establishment of riparian vegetation throughout the project due to streamside plantings and improved grazing practices.
In 2005, ambient temperatures and recorded stream temperatures at most locations in late summer were comparable to previous years. Fish were further protected from high water temperatures by the cold-water refugia provided by the deep pools created throughout the project. No substantial fish mortality was reported by Three Forks Ranch personnel who frequently observed the fish throughout the most critical summer period.
In the fifth full growing season following construction, vegetation continues to re-establish along channel margins and floodplain surfaces. Grasses and forbs are the primary vegetation types colonizing the banks and riparian zone. This is evident along most of the project, even along many of the reshaped gravel and cobble bars. Willows (Salix spp.) are the predominant woody vegetation establishing along channel margins, and gravel and cobble bars. Changes in the willow assemblages can be characterized in two general ways. First, many transplanted willows have experienced some dieback, but there is new growth at the bases of the plants. This was first noted in previous years along the project and new growth of transplanted willows has continued. We expect that, given relatively normal precipitation and flow conditions, these plants will continue to successfully regenerate with proper grazing practices. Second, willows are colonizing many of the exposed gravel bars and cobble bars. While many of the early colonizers have established in locations that will not support perennial vegetation over the long term (i.e., too low into the active channel where excessive periods of inundation and high shear stresses preclude long-term establishment), a large number of more suitable sites have been successfully colonized. These locations are expected to develop into an important functional component of the riparian community. Willow, grass, and forb establishment will increasingly contribute to the overall geomorphic stability of the channel, as well as improve the available cover for aquatic fauna, input coarse particulate matter for desirable aquatic insects, and reduce water temperatures through shading.

Factors limiting recovery of the ecosystem: The restoration reaches, like all streams, continue to be influenced by upstream land management practices. Upstream of the South Fork restoration reach and beyond the Three Forks Ranch property boundary, existing grazing practices increase fine sediment loading and channel instability through continual disturbance of streamside vegetation and soils. The restoration reaches cannot be assessed without considering the overall watershed, and the potential effects of upstream grazing practices on downstream reaches are a continuing point of concern. A sediment trap constructed above the project on the South Fork will require periodic maintenance to ensure its long-term effectiveness.

Socio-Economic & Community Outcomes Achieved

Key Lessons Learned

An interesting sidelight of this project is the desire of some downstream neighbors to restore another sixteen miles of the Little Snake River. Three Forks Ranch has agreed to fund the Rosgen master plan for this next length of river and to help these neighbors obtain funding from governmental agencies. The Natural Resources Conservation Service, US Fish & Wildlife Service, Wyoming Game and Fish, and Colorado Division of Wildlife are all assisting in making the next phase of the project a reality.

Long-Term Management

Three Forks Ranch is presently working with Wyoming Game and Fish, the Colorado Division of Wildlife and the US Forest Service to commit a portion of the project to aiding the Colorado River cutthroat trout. During the project, several ponds were created that can be easily isolated from the main flow of the river using fish barriers. These ponds have been offered to the above mentioned agencies for use as brood ponds to raise Colorado River cutthroat trout for transplanting elsewhere.

Because Three Forks Ranch has a large cattle operation, a high-intensity/low-duration grazing system in the South Fork had to be developed. The South Fork was split into five small pastures, which are used only in the spring. Approximately 2000-3000 yearlings are put in each of these pastures for durations running from 3 to 10 days, depending on the size of the pasture. This plan uses the South Fork early in the spring, allowing it to recover while there is plenty of growing season left. It is also the least destructive time of the year to graze the willow population. The cattle seem to spread out on their own this time of year when both the upland and riparian vegetation is green and lush, as opposed to later in the year, when only the riparian areas are green. Also, water is plentiful in the spring and cattle do not have to return to the South Fork for water. This system has worked well for five seasons now. The willow population is thriving. The weeklong hoof-shear has 51 weeks to heal before the cattle return, and the fishery in the South Fork has not been negatively impacted.

The North Fork, Middle Fork, and main stem have been removed from grazing for the last five seasons. However, ranch managers are contemplating some early spring or late fall use of these pastures also, in order to remove decadent grass populations and help regenerate growth. If deemed appropriate, these areas would probably be grazed once every three years.

Sources and Amounts of Funding

5,000,000 USD This project was funded by David Pratt, the owner of Three Forks Ranch.